US ambassador to Japan John Roos (centre) is surrounded by reporters after his meeting with Japanese Senior Vice Foreign Minister Shuji Kira in Tokyo on Wednesday. Photo: AFP

The United States ambassador to Japan vowed “complete and unequivocal cooperation” on Wednesday over the alleged rape of a local woman by two servicemen on an island fed up with hosting the US military.

Ambassador John Roos moved swiftly to reassure people on the southern Japanese island of Okinawa that he shared their anger over an incident that has the potential to act as a lightning rod for growing anti-US feeling.

Roos said the US government and military would “provide full, complete and unequivocal cooperation to the Japanese authorities in their investigation”.

After a meeting with vice foreign minister Shuji Kira, who is standing in while Foreign Minister Koichiro Gemba is in Europe, Roos said: “I do understand the anger that many people feel with respect to this reported incident.”

He said he wanted the Japanese people to know that he shared that anger.

Okinawa governor Hirokazu Nakaima, a vocal critic of the size of the vast US presence on the island, met Defence Minister Satoshi Morimoto and expressed his fury, describing the alleged crime as “insane”.

The arrest of the two men on Tuesday is a potential flashpoint in relations between the US military and their reluctant Okinawan hosts.

Previous incidents have sparked angry large-scale demonstrations, with participants demanding a cutting back of the US presence. Around half of the 47,000 military personnel Washington has in Japan are based in Okinawa.

Relations at the moment are especially prickly, with locals resentful of the deployment of 12 tilt-rotor Osprey aircraft.

Ostensibly, the objections centre on the Osprey’s perceived poor safety record, but commentators say it is a proxy issue for islanders fed up with what they see as an unequal burden and calling for mainland Japan to step up to the plate.

Despite the groundswell of opinion, the strategic importance of the Okinawan archipelago, which strings out from the Japanese mainland to Taiwan, makes it a vital bulwark against the rising might of China.

Neither Washington nor Tokyo, which depends on its ally for defence, is able to countenance a large-scale US drawdown from the area.

The leading Mainichi Shimbun daily said the two servicemen, both aged 23, had flown to Okinawa on Sunday and were arrested hours before they planned to leave on Tuesday.

The paper, citing police sources, said they had allegedly approached the woman on the street and sexually assaulted her. The woman suffered injuries to the neck, it said.